Water flows through a pipe with a velocity given by $\overrightarrow{V}= \big( \frac{4}{t}+x+y \big) \hat{j} \: m/s$, where $\hat{j}$ is teh unit vector in the $y$ direction, $t(>0)$ is in seconds, and $x$ and $y$ are in meters. The magnitude of total acceleration at the point $(x,y)=(1,1)$ at $t=2\: s$ is ______$m/s^2$